Technical Abstract:
Monocyte-derived dendritic cells (MoDC) from peripheral blood of humans, mice, and pigs are obtained by culturing PBMC with a combination of IL4 and GM-CSF. However, while IL4 is a major Th2 cytokine in man and mouse, this cytokine is rarely detected in the peripheral lymphoid organs of swine. Contrarily, IL13 is readily expressed by porcine white blood cells. The successful use of IL4 to generate MoDC in pigs is likely due to the existence of a common receptor for IL13 and IL4 and the fact that these cytokines have redundant functions in many species despite less than 25% structural homology within any given species. In our laboratory we have expressed porcine IL13 and successfully generated MoDC with similar morphological and functional characteristics as described in literature. Porcine MoDC were characterized as having the predicted expression of T cell costimulatory molecules, the ability to process and present antigen, and the unique ability to stimulate a primary mixed lymphocyte response in vitro. The innate immune response to PolyI:C (TLR 3 ligand), LPS (TLR4 ligand) was tested with no induction of type I interferons by LPS but a strong response to PolyIC. IL13/GM-CSF MoDCs produced significant levels of IFN alpha in response to an attenuated derivative of the ssRNA virus, FMDV (LLA12) and lower levels of this cytokine in response to virulent FMDV. UV inactivation of the virus eliminated FMDV mediated induction of interferon alpha. These results indicate that the RNA binding TLRs (TLR 3,7 and/or 8) may mediate early, innate immune responses to FMDV by circulating, MoDC.